Having grown up on the Gulf of Mexico, even San Diego in August is crazy cold. Brrrrrrrrrrr...
Confession; I haven't gone into the water in SD. My brother tells me the beaches are boring, and every time he drops someone off at a beach they are calling him in half an hour to pick them up because it's so boring. I think that HE doesn't like the beach, and wants them to come back and hang out with him, so he takes them to awful beaches LOL. Since I'd rather hang out at his house in his pool and his hot tub drinking his beer, we don't bother with beaches there.
And we grew up in San Jose with a dad in Santa Cruz, so...brr.
I should specify that I'm not talking about the ocean temp. I dont really swim in the ocean. I am talking about swimming in the ship pools and also laying out on the beach at CC. Is it hot enough to do those things?
Feb 2013, late Jan 2014, Jan 2015 we were out in the sunshine just fine at CC. Was lovely. Far better than the October cruise where the sun, apparently, was 2 miles away and I'm quite sure I know the exact spot that I'll eventually get skin cancer from the burn I got (left upper thigh...there is STILL a marked difference in my skin color on that side vs the right side that wasn't directly in the sun...it's scary)...and that was from one hour, WITH sunscreen, in the sun. Yipes.
Feb 2012, given how cold it was in FL and how cold my cousins were on the ship and CC (same cousins that enjoyed CC with us the following year), I doubt we could have been on loungers in bathing suits on CC.
I don't sit in the pools on Disney ships, so I don't know about that. (they are too small to "swim" in)
I am now giving up January trips to WDW and Universal (the potential for actual freezing cold weather is too high in our experience) but I'd still take a late Jan, all Feb, all March trip to the Caribbean. and we do, in fact, have a March Carib cruise planned out next year. I anticipate much warmth and fun. And since I do swim on the much bigger Royal ships (though Freedom doesn't have a heated pool), I anticipate swimming then and perhaps going in the water on CocoCay, at St Maarten, and St Thomas.